Earlier this year, we produced a video documenting Academy researcher Luiz Rocha’s work in Belize studying invasive lionfish. These predators, originally from the Indo-Pacific, found their way to the northwest Atlantic in the 1990s—likely through an aquarium release—and have steadily moved south over the past fifteen years.

The lionfish are wreaking havoc in the area because they voraciously gobble up smaller, native fish—threatening everything from coral reef ecosystems to local economies based on fishing and tourism. In addition, eradication appears impossible and whatever is keeping them in check in their native Indo-Pacific habitats—researchers around the world are trying to find out what—appears to missing in the Atlantic.

“Prey in the Indo-Pacific could simply be more aware of the danger lionfish pose,” Rocha says. “There could also be parasites keeping the lionfish in check in their native habitats.”

Bad
A recent study in PLoS One determines that humans may be the only threat to lionfish in their new home. An international research team looked at whether native reef predators such as sharks and groupers could help control the population growth of lionfish in the Caribbean, either by eating them or out-competing them for prey.

The team surveyed 71 reefs over three years, in three different regions of the Caribbean. Their results indicate there is no relationship between the density of lionfish and that of native predators, suggesting that, “interactions with native predators do not influence” the number of lionfish in those areas.

The researchers did find that lionfish populations were smaller in protected reefs, but researchers attributed the lower numbers to targeted removal by reef managers, rather than consumption by large fishes in the protected areas. As Rocha mentioned in the video last spring, encouraging the hunting and human consumption of these spiny fish may be reefs’ only hope.

Ugly
Recent submersible dives deep off the coast of Fort Lauderdale, Florida reveal that these invasive lionfish populations aren’t just spreading southward—they’re also heading to great depths, out of the reach of their only predators, human hunters.

“We expected some populations of lionfish at that depth [300 feet], but their numbers and size were a surprise,” says Stephanie Green, of Oregon State University, who participated in the dives.

The lionfish are growing to an unusually large size—as much as 16 inches. “A lionfish will eat almost any fish smaller than it is,” Green says. “Regarding the large fish we observed in the submersible dives, a real concern is that they could migrate to shallower depths as well and eat many of the fish there. And the control measures we’re using at shallower depths—catch them and let people eat them—are not as practical at great depth.”

Rocha confirms this. “Even if control efforts are successful in shallow water, we can’t reach these deep fish.” And the lionfish at great depths can easily move to shallower areas. In addition, “these larger fish produce more eggs,” Rocha says, creating even larger populations.

(Rocha is hoping to join on subsequent dives. He was invited on this recent submersible dive, but was attending a conference on Indo-Pacific fish in Japan at the time. A video of the dives is available here.)

Good
We want to end on an upbeat note, and Rocha has a recent study in Marine Ecology Progress Series about the spread of lionfish down the coast of South America and into Brazil. The fish haven’t reached that far yet, but given their rapid spread, it seems to be only a matter of time.

Working with other Brazilian researchers, Rocha investigated movements of various fish species across the Amazon-Orinoco plume (AOP), where the Amazon and Orinoco rivers meet the Atlantic Ocean. The study describes the AOP as “a large freshwater and sediment runoff between the Caribbean and the Brazilian Provinces that represents a ‘porous’ barrier to dispersal for reef organisms.”

The scientists found that while a few “vagrant” species recently crossed the barrier heading north, “species headed south don’t spread as quickly,” according to Rocha. “The currents make it tricky to cross.”

This could be the first bit of good news in stopping the spread of lionfish. “This means we can keep an eye on it and control the lionfish as they cross, keeping their numbers down,” Rocha says.

Next
Rocha and colleagues here at the Academy and in Europe are beginning a population genomic study of the invasive lionfish. This study will look at fine-scale genetic diversity of lionfish among the different Caribbean islands. Rocha will start collecting samples in two weeks in Curaçao. The samples will then be analyzed by Academy researchers—including Rocha’s wife, Claudia—here at the Center for Comparative Genomics.

“We want to see if there is gene exchange between different island populations,” Rocha explains. “This will help us determine how successful local efforts to control lionfish can be if larvae are coming from other locations. This study can help inform how resources are used to control different populations.”

The fight against invasive lionfish continues…

Image: Alexander Vasenin/Wikipedia

In ecosystems, every organism plays a part. From the smallest microbe to the fiercest predator to the tallest tree, each species contributes to making its community healthy. But this role isn’t always obvious.

Take the colorful toucan and the palm tree Euterpe edulis in the Brazilian rainforest. Scientists have long understood that the palm’s seeds are dispersed by not only the large birds, but smaller birds, too. The birds eat the seeds, fly-off and poop—spreading the palm seeds far and wide.

But the past 100 years have seen many changes in the rainforest. Since the 1800s, the forest has become more and more fragmented, mostly due to agricultural development such as the planting of coffee and sugar cane. By creating this patchwork of forest and farmland, humans have affected the rainforest in many ways.

According to a new study in the journal Science, the numbers of toucans have declined in the forest patches, and the palm trees in those areas have responded by producing much smaller seeds.

These palms generally produce different-sized seeds. Different sized-birds with different-sized beaks distribute the seeds evenly. But with the toucan and other large birds, such as large cotingas, absent from the ecosystem, only the small-seeded palm trees are reproducing. The birds are basically changing the evolutionary trajectory of these trees.

Researchers, led by Mauro Galetti from the Universidade Estadual Paulista in São Paulo, Brazil, collected more than 9,000 seeds from 22 different palm populations and used a combination of statistics, genetics, and evolutionary models to determine that forest fragmentation displaced many toucans. They also considered the influence many environmental factors, such as climate, soil fertility, and forest cover, but none could account for the change in palm seed size over the years in the fragmented forests.

For palm tree seeds, size matters. “Small seeds are more vulnerable to desiccation and cannot withstand projected climate change,” explains Galetti. The rainforest is projected to be drier as the climate warms, and the smaller seeds are less equipped than larger seeds for survival in these conditions.

See, every organism plays an important part.

“Unfortunately, the effect we document in our work is probably not an isolated case,” says Galetti. “The pervasive, fast-paced extirpation of large vertebrates in their natural habitats is very likely causing unprecedented changes in the evolutionary trajectories of many tropical species.”

Image: Lindolfo Souto

Brazil leads the world in the use of biofuels instead of gasoline. About a quarter of their automobile fuel consumption comes from sugarcane, which significantly reduces carbon dioxide emissions that otherwise would be emitted.

Scientists wondered how the local climate has been affected as sugarcane has quickly displaced other agriculture in the region.

Using maps and data from hundreds of satellite images, the researchers calculated the temperature, the amount of water given off, and how much light was reflected versus absorbed for each of the different types of vegetation. They found that, compared to land cultivated with other annual crops, sugarcane reduced the local air temperature by an average of 0.93 degrees Celsius (1.67°F).

But compared to the natural vegetation of central Brazil—mainly grass and shrubs—the sugarcane fields warmed the ambient air by 1.55°C (2.79°F).

Co-author David Lobell of Stanford says the bulk of the temperature difference results from evapotranspiration—the moisture released to the air through the leaves of the plants and the soil.

The researchers emphasize that the beneficial effects only apply if sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.

So far, most of the conventional thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions. But according to co-author Greg Asner of Carnegie, “It‘s becoming increasingly clear that direct climate effects on local climate from land-use decisions constitute significant impacts that need to be considered core elements of human-caused climate change.”

Image by Rufino Uribe/Wikimedia